You can invest in a mix of debt and equity funds based on your risk profile. Within equity, this can be further subdivided into large cap, midcap, multicap and small cap. Check here for a free risk profile.
The best funds to invest in each of these fund classes are listed on any good investment website. You can also check out https://www.jama.co.in/direct-mutual-funds/explore/?category=y&class=equity for a list of direct plan funds.
If you invest about Rs 10k as a SIP monthly, you can gain a significant amount over 20 years. See an illustration below. Invest in direct plan funds always.
